Method of separating a sheet into chips

ABSTRACT

Method of separating a sheet into chips for use in the formation of a floor covering. Plastic particles are calendered into a sheet which is cooled by a cooling bath. The sheet is fed into a slitter which places intermittent cross-machine direction slits in the sheet. The sheet is then fed into a grinder where the knife-hammers traveling at high speed fracture the sheet into irregularly shaped chips.

United States Patent Inventor Virgil Spencer Lancaster, Pa.

Appl, No. 871,284

Filed Nov. 13, 1969 Division of Ser. No. 658,675 Aug. 7, 1967, Pat. No. 3,527,418

Armstrong Cork Company Lancaster, Pa.

Patented Assignee METHOD OF SEPARATING A SHEET INTO CHIPS 1 Claim, 4 Drawing Figs.

U.S.C1 241 25, 241/3 Int. Cl ..B02c 18/06, B02c 18/44 [50] Field ofSearch 241/3,15, 17, 25, 27, 154 (Cursory), 222 (Cursory), 301 (Cursory); 18/1 (B), 1 (E) [56] References Cited UNITED STATES PATENTS 2,559,701 7/1951 Becker 241/222 3,031,745 5/1962 Dzialo 241/301X 3,217,988 11/1965 Lightfoot 241/154X Primary Examiner-Donald G. Kelly AttarneyClifford B. Price ABSTRACT: Method of separating a sheet into chips for use in the formation of a floor covering. Plastic particles are calendered into a sheet which is cooled by a cooling bath. The sheet is fed into a slitter which places intermittent cross-machine direction slits in the sheet. The sheet is then fed into a grinder where the knife-hammers traveling at high speed fracture the sheet into irregularly shaped chips.

Patented May 25, 1971 2 Sheets-Sheet l INVENTOR Vl RGI L SPENCER ATTORNEY Patentd May 25, 1971 2 Sheets-Sheet 2 PRIOR ART INVENTOR VIRGIL SPENCER BY W M ATTORNEY METHOD OF SEPARATING A SHEET INTO CHIPS CROSS REFERENCE TO RELATED APPLICATION This application is a division of Ser. No. 658,675, filed Aug. 7, l967, now Pat. No. 3,527,418, issued Sept. 8, 1970.

BACKGROUND OF THE INVENTION 1. Field ofthe Invention The invention is directed towards a method of reducing a sheet material into a plurality of chips. The chips are formed by fracturing the sheet material into a plurality of small particles. The chips may then later be used to form the design of a floor covering material.

2. Description of the Prior Art A number of different methods of reducing a sheet material to a chip structure are shown in US. Pat. Nos. 2,145,862; 2,516,295; and 2,60l,200. In the first-mentioned Patent the sheet is shredded by passing the sheet through a set of rollers, one being adjusted to rotate at a rate substantially greater than the other. In the second-mentioned Patent a brittle sheet is fed between two sawtooth crushers which chop the sheet into a plurality of pieces. In the third patent there is disclosed a ship forming structure which uses a single high-speed cutter to cut a sheet material into a plurality of small pieces.

Another common method of forming chips is to separate the sheet into a plurality of small squares. The square pieces are then fed into the grinder which shatters the squares to form the plurality of small chips.

The primary problem with the previously mentioned prior art method is the formation of a large number of chips with one straight side and some chips with two straight sides at a right angle. With the methods set forth in the above patents, there exists a problem in the controlling of the size of the chips so as to secure a more or less uniform gradation of uniform sizes.

SUMMARY OF THE INVENTION The invention herein provides for a relative size control because the intermittent slits serve to prevent formation of excessively large chips. The provision of the intermittent slits in the rigid sheet has the effect of controlling the fracture pattern and prevents the generation of large chips.

The sheet material is formed and then cooled to provide it with a sufi'lcient degree of rigidity. The slits are then placed in the sheet, but due to their positioning andthe use of a backup roller merely form the slits in the sheet and do not tend to shatter the sheet into chips. The sheet with slits is then fed towards highspeed knife-hammers which strike the relatively unsupported sheet and fracture or shatter the sheet into a plurality of small chips. The slits control the degree of fracturing and the size of chips generated.

The use of intermittent slits, rather than the formation of square pieces, reduces the number of square edges on the material approaching the grinder and, consequently, reduces the number of chips formed with straight edges. The chip structure, as used in a flooring material, should have an irregular shape to provide the most aesthetically pleasing appearance. The use of chips with straight edges tends to distract from the aesthetic appearance.

Finally, the invention herein reduces the number of manufacturing steps since there is no need now to form individual square pieces for processing by the grinder containing the knife-hammers.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a side view of the total apparatus for separating a sheet into chips;

FIG. 2 is a prospective view of the principal elements used to form chips;

FIG. 3 is a typical pattern breakdown using the process of this application; and

FIG. 4 is a typical pattern breakdown using customary prior art processes.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I there is shown a layout of the apparatus used to form the sheet material and then separate the sheet material into chips. A conventional calender roll structure 2 is used to form the sheet material. The plastic particles 4 are fed between the rollers 5 and 6 of the calender roll structure. The particles are pressed into a sheet and then by means of a doctor blade 8 stripped from the upper roller 5.

The sheet 10 is fed into a chilled water bath 12 to harden the plastic material and form a brittle sheet structure. As the sheet material leaves the water bath 12 an air squeegee structure 14 blows the excess water off the sheet material.

The sheet material then passes to the scorer or slitter which is composed of two rolls l7 and 18. Roll 17 has intermittently spaced blunt or knife-edge blades on its outer periphery which engage with the sheet material to crack or slit the sheet to form the slits. The backup roll 18 has recesses which are correspondingly placed relative to the blades of the roll 17. As seen in FIG. 2 the slitter structure places intermittent slits 19 in the sheet material. The slits are intermittently spaced in a straight-line pattern crosswise of the direction of sheet travel. The slits are also alternately spaced relative to the next adjacent row of slits.

The sheet material with its slit structure now passes onto the grinder 20. The grinder has a plurality of knives or hammers 21 circumferentially spaced around the periphery of the roller that carries the knives of the grinder. The knives 21 engage the sheet material as it is fed towards the grinder, and when they strike the sheet in its brittle state, cause the sheet to shatter into a plurality of small chips (see FIG. 3). The perforated screen 22 acts as a size grading grid and permits the properly sized chips 24 to pass therethrough into a collection chamber 26. Any oversize chips retained in the region between the grinder roll and its knives and the perforated screen 22 are further reduced in size by being subsequently struck by the knives 21.

FIG. 4 shows the chip breakdown pattern of the conventional square particle used in the prior art techniques. The chip breakdown pattern clearly shows that a large number of the chips will have one and, in some cases, two straight sides. Particularly those chips with the two straight sides forming a corner have been found objectionable in a floor covering. The chips, when spread out in a random pattern to form a chip design for the flooring, have their best aesthetic appearance when all the chips are irregular in shape. The existence of a large member of chips with straight edges, and particularly chips with two straight edges at a 90 angle, provides a flooring design that does not give a pleasing aesthetic appearance.

As seen in FIG. 3, the chip breakdown pattern of this invention has no two straight-edge 90 angle chip structures formed and has a minimum of chips formed with one straight edge. This structure more nearly approaches the irregular contour that one expects to see when one is simulating a ground stone pattern.

A preferred plastic for use with this process is a polyvinyl chloride homopolymer composition. With this plastic, a water bath of 50 F. is used and the grinder, which is a conventional Taylor Stiles giant mill, is run at 850 revolutions per minute. The slitter produces slits in the sheet material that are l /inches long and l /inches apart. The apparatus produces chips of one-fourth inch to three-fourth inch in size.

The particular plastic used determines the cooling bath temperature so that the sheet material is brittle enough to shatter when struck a blow by the knives of the grinder. The slits can be spaced from one-half inch to 2 inches apart and this spacing will affect the size of the chips produced. Other plastics may be used, for example: a polyvinyl chloride copolymer, a polyvinyl acetate, or a combination polyvinyl chloride copolymer and homopolymer. In addition, all the above plastics may be unfilled or filled to various percentages.

The above is a description of a preferred embodiment and some alternate plastics that may be used, but the invention is to be limited to only that which is set forth in the claim.

crosswise and lengthwise of the sheet material, subjecting the sheet material to a plurality of high-speed knives to fracture the sheet into a plurality of small chips. 

